Instant Messaging (IM) is one of the easiest and most cost effective ways of communicating interactively over a network such as the Internet. In its most basic form, IM enables users to locate and establish an independent chat session with one another. Once connected with one another, IM users can discourse textually in near real time and carry out other operations, such as the sharing of files. The nature of an IM communication is less obtrusive than a phone call and consequently IM has found its niche among other more common forms of communication. It is very well suited to immediate, informal exchanges of information among users in a distributed group. IM is integrated easily with the desktop environment (the clients usually only require limited processing power) and can be used as part of a pallet of personal or business communications.
One aspect of IM is presence, i.e. a dynamic profile of one person (user), visible to others. Presence makes available a user's status to others and the status of others is available to that user and can be used for multiple purposes, such as to control the user's own communication, to share relevant information with other users, to manage the impression a user makes on others or, for example, to control network-based services. Typical data which might be made available through presence include a user's activity (on the phone, absent, appointment, holiday, meal, meeting, in-transit, travel, vacation, busy, etc.), his location (home, office, etc.), the means that can be used to communicate with the user (chat, call, send picture, etc.) and the mood of the user (happy, sad, angry, etc.).
In addition, applications and services (for example, Push To Talk (PTT), advertising, weather service) can also publish or use presence. In a broader view, devices, places, and other things also might have a presence. In particular, presence is an indication to other users concerning a particular user's online status.
In a mobile environment, presence makes communication more effective by allowing a mobile user to see whether another party is available and what is the most suitable way to contact that person (for example, place a call, PTT the person, or send a message). Not only can individual users publish their presence, but companies and applications can use presence for advertising and as an information channel. Presence also provides a user with a degree of self-expression by enabling users to personalize how they appear on other devices. Additional services such as online games may also make use of presence information.
IM clients typically allow a user to maintain contact details of people that he/she wishes to hold IM conversations with, or whose presence the user wishes to be informed about. These contacts are known as “buddies”. As a result, presence and buddy lists are closely associated. A buddy list is a list of known users whose presence is indicated. If a user is online and available to receive a message, this information will be displayed to other users who have subscribed to that user's presence information, typically using an indicative icon or the like on the user's display. By selecting the name of the user, for example using a double click of a pointing device, an IM can be sent in near real-time. Therefore, through the use of presence, a user can tell immediately which of his buddies is contactable, unlike a telephone where a party must call another party in order to see if he is contactable.
One drawback of existing IM systems is that they are proprietary in nature and interoperability between the IM products of one supplier or operator are typically unable to operate with the products of another supplier or operator. To address this problem, the OMA has developed the IMPS 1.x series of technical specifications and service frameworks which, if conformed to by a supplier in the development of their products or operator in the provision of IMPS services, ensure interoperability. The OMA IMPS 1.x series of technical specifications and service frameworks have been largely accepted and implemented by many suppliers and operators and it currently provides the sole IMPS service platform.
The emerging broadband Universal Mobile Telecommunications System (UMTS), or “third-generation (3G),” provides for the packet-based transmission of text, digitized voice, video, and multimedia at high data rates and has the objective of providing a consistent set of services to mobile computer and phone users throughout the world. SIMPLE and specifically SIP (Session Initiation Protocol) has been selected to provide the IMPS infrastructure within 3G networks. SIMPLE is not directly compatible with OMA IMPS 1.x and, as a result, when suppliers and operators start deploying SIMPLE compliant infrastructures, there will be a need for the existing OMA IMPS 1.x infrastructures to interwork with the SIMPLE infrastructures.